1. Field of the Invention
This invention relates to an image coding technology, and it particularly relates to method and apparatus for evaluating the quality of an image during the coding process.
2. Description of the Related Art
During the 1990's in particular, the widespread use of PCs (personal computers) and other information equipment, the popularization of digital cameras, color printers and so forth and the explosive increase in the use of the Internet accounted for a deep infiltration of the culture of digital images into the everyday life of ordinary people. Under these circumstances, coding and compression technologies such as JPEG (Joint Photographic Experts Group) for static images and MPEG (Moving Picture Experts Group) for moving images, have been standardized so as to improve the facility of distribution and reproduction of images through recording media such as CD-ROMs, and transmission media such as networks and broadcasting waves.
In the JPEG series, JPEG 2000 using discrete wavelet transform (DWT) has been standardized in order to achieve further improvement of compression efficiency as well as to attain high image quality. DWT replaces discrete cosine transform (DCT) which conducts a filtering on the image on a block basis and plays an important role in the performance of compressing the image in JPEG 2000. In addition, in MPEG, the same wavelet transform is employed in texture compression.
The digital camera and camcorder have been miniaturized and rendered multifunctional and the convenience of their use has been greatly improved. On the other hand, because of the light weight of the camera body and the high magnification of the optical zoom, it is very difficult for novice users to avoid the bad effects of camera shake during shooting. In addition, although the resolution of the image is increased very rapidly because of the high density of CCD, such high resolution is not much use when the bad effects caused by camera shake prevail. It therefore becomes meaningless to pursue the enhancement of the performance of the products.
Moreover, when motion pictures are shot for long periods by a security camera or the like, the image data are stored in a large storage device, and motion frames with bad image quality such as poor focus can waste this storage space.